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Painful Pops and Cracks in Knees

Question:

My knee pops out consistently when I work out. I'm 19 years old, at a healthy weight,
and have an active lifestyle. I have quit working out several times due to painful
cracks and pops. Is there anything that I can do to prevent this from happening?

Answer:

A knee that decides to "pop" or make cracking sounds can be quite alarming. I think
that all of us at one time or another have kneeled down and had our knees make a loud
noise, but no pain occurs. In the majority of instances, though, this is a harmless
soft tissue band that rubs in an unusual way within the knee joint, makes a sound,
but doesn't hurt or cause any damage. On the other hand, what is being described in
this question deals with a painful "crack" or "pop" in the knee. There are multiple
possible causes of this.

The knee joint internally is covered with cartilage
- the same pearly white covering that we see on the end of a turkey or chicken bone.
This cartilage protects the joint as we flex, bend, and straighten the knee for millions
of cycles over our lifetimes. If this cartilage becomes worn or frayed, the normal
smooth sensation that accompanies bending the knee can become rough - leading to catches
or popping sensations. If the cartilage becomes severely damaged (almost like having
a pothole on a highway) then severe painful catches and swelling can occur.

Other possible causes of "mechanical" symptoms in the knee include meniscus tears
or loose bodies in the knee. The meniscus is another type of cartilage that acts as
the shock absorber of the knee. The medial meniscus lies on the inner aspect of the
knee between the cartilage ends of the thigh bone and leg bone, while the lateral
meniscus is on the outer side. For someone with a history of a knee-twisting injury
or accident, tears of the meniscus are quite common. If the tear is severe enough,
then the knee can actually lock solidly in one position -- leaving the person unable
to bend or straighten without a physicians help. Luckily, these severe tears are not
common, but smaller tears, leading to a catching sensation and pain, are seen routinely
in an orthopedic surgeon's office.

Loose bodies are small fragments of
cartilage or other tissue that move freely around the joint and cause complaints of
popping and catching. Theses are normally seen well with MRI or x-ray, and patients
respond very well to small surgeries that remove the fragments.

Finally,
for young, active patients with these complaints (and no history of injury), the most
common diagnosis involves the knee cap. As patients work out on the elliptical machine
or stair master, for instance, the kneecap is moving back and forth through a groove
on the end of the thigh bone. If the knee cap isn't covered by a smooth surface of
cartilage (a condition called chondromalacia) the popping and catching can be painful
and frustrating. If the knee cap has poor muscular control, then it even may start
to jump out of the groove causing a "my knee just popped out" sensation. Both of these
problems may be accompanied by swelling, pain and inability to be active.

In all of these situations, it's important to consider the following: mechanical
symptoms (popping, catching, or locking) that follow an injury to the knee or that
are noted with significant swelling need to be addressed by a health care provider.
Many times, knee x-rays and MRI's help to confirm a diagnosis. Otherwise, keeping
the quadriceps (thigh) muscles strong with exercises and possibly physical therapy
can alleviate many of these complaints.

I recently heard about a new knee procedure that uses medical separators rather than
total knee replacement to relieve pain from osteoarthritis degeneration. Can you tell
me about this and where to find out about getting it done?